Radio resource management and admission control are fundamental features of a radio communications system sharing radio resources between users, user sessions and radio bearers.
In packet data communications, transport protocols, such as TCP, involving congestion control are widely used.
The Internet Society: Request for Comments (RFC) No. 793, Transmission Control Protocol, DARPA Internet Program Protocol Specification, September 1981 describes the functions to be performed by the Transmission Control Protocol (TCP), the program that implements it, and its interface to programs or users that require its services.
The Internet program protocol specification discusses a receiver advertised window, rwnd, used e.g. in congestion control and the impact of a shrinking rwnd. It also discusses how TCP should operate in relation to rwnd.
The Internet Society: Request for Comments (RFC) No. 2581, April 1999 specifies in detail TCP congestion control. One of the control parameters is the congestion window, cwnd, another is the advertised receiver window, rwnd.
During Congestion Avoidance cwnd is increased in relation to round-trip time until a packet loss is detected, which is interpreted as congestion. This is e.g. the case if a retransmission timer times out without a packet being acknowledged during the retransmission time of the packet.
At the beginning of a data transfer TCP probes the network for its conditions. For each (positively) acknowledged data packet, the sender-side increases cwnd until it reaches a threshold ssthresh. During data transfer cwnd and ssthresh are adapted in relation to received acknowledgements.
The advertised receiver window, rwnd, is transmitted together with acknowledgments from TCP receiver to TCP sender, acknowledging received TCP packets.
The RFC also defines the concepts segment, receiver maximum segment size, RMSS, and sender maximum segment size, SMSS. cwnd is an integer multiple of SMSS.
A segment is any TCP/IP data or acknowledgment packet (or both). The RMSS is the size of the largest segment the receiver is willing to accept. The SMSS is the size of the largest segment that the sender can transmit. SMSS can be set to the maximum transmission unit, MTU, of the network, a path MTU (see below) or RMSS.
The Internet Society: Request for Comments (RFC) No. 1191, November 1990 describes a technique for dynamically discovering a maximum transmission unit, MTU, of an arbitrary Internet path. A path MTU, PMTU, is the minimum of the MTUs of each hop of the path. Upon receipt of a “Datagram too big” message, the host reduces initially assumed PMTU for the path. RFC1191 suggests that also MTU size is reported in association with the “Datagram too big” message. Normally, if the route changes and the new PMTU is lower, it will be discovered. For detection of increased PMTU, the segment size can be increased periodically. The RFC discusses TCP actions and management interface.
The Internet Society: Request for Comments (RFC) No. 3150, July 2001 discusses interactions between TCP Congestion Control and TCP Buffer Auto-tuning. The RFC recommends that if a host is connected over links of different speeds at different times, the host may use receive buffer auto-tuning to adjust the advertised window to an appropriate value.
R. W. Stevens: TCP/IP Illustrated, Volume 1, Addison-Wesley, Reading Mass., 1994, describes in section 1.2 layering of networking protocols and the combination of different protocols into a protocol suite. Stevens describes a 4-layer system with layers                link layer,        network layer,        transport layer, and        application layer.        
The link layer is also called data link layer, and could e.g. include a device driver in an operating system of a computer. The network layer handles packet movements such as packet routing. Examples of the network layer include IP (Internet Protocol), ICMP (Internet Control Message Protocol), and IGMP (Internet Group Management Protocol). The transport layer concerns' data flows between two hosts. Examples of transport layer protocols are TCP (Transport Control Protocol) and UDP (User Datagram Protocol). The application layer handles application details. Well-known exemplary application layer protocols are FTP (File Transfer Protocol) and SMTP (Simple Mail Transfer Protocol).
P. Kuhlberg: Effect of Delays and Packet Drops on TCP-based Wireless Data Communication, Master's Thesis, University of Helsinki, Dept. of Computer Science, December 2000, discusses in appendix D topics to be further investigated. Included is investigation of receiver window impact on TCP performance.
P. Sarolahti, A. Gurtov, P. Kuhlberg, M. Kojo, K. Raati-kainen: Tuning TCP Advertised Window for Bottleneck Links with Variable Delays, to appear in ICC 2002, April 2002 suggests halving the advertised window for each connection when a new TCP connection starts using a bottleneck link in parallel with an existing TCP connection and maintenance of a common window space for all connections to a mobile station based on link bandwidth-delay estimation at receiver. Each TCP connection gets to advertise its fair share of the shared window space.
3rd Generation Partnership Project (3GPP), Technical Specification Group Radio Access Network, Radio Resource Management Strategies, 3GPP TS 25.922 v3.6.0, France, September 2001, illustrates in section 6.3 some scenarios of Admission Control in relation to radio resource management, RRM. Radio bearer control is described in section 7.
Within this patent application, a radio network controller, RNC, is understood as a network element including an RRM (Radio Resource Management) entity. The RNC is connected to a fixed network. Node B is a logical node responsible for radio transmission/reception in one or more cells to/from a User Equipment. A base station, BS, is a physical entity representing Node B. A server device provides information accessible to other devices over a communications network such as, e.g., the Internet.
With reference to FIG. 1, base stations <<BS 1>> and <<BS 2>> are physical entities representing Nodes B <<Node B 1>> and <<Node B 2>> respectively. <<Node B 1>> and <<Node B 2>> terminate the air interface, called Uu interface within UMTS, between UE and respective Node B towards the radio network controller <<RNC>>. <<RNC>> is connected to a fixed network <<Network>>. The fixed network may comprise one or more Server Devices <<Server Device>>.
In FIG. 1, the base stations are connected to the same radio network controller RNC. However, this specification also covers the exemplary situation where the base stations are connected to different RNCs. In UMTS, the RLC protocol is terminated in a serving RNC, SRNC, responsible for interconnecting the radio access network of UMTS to a core network.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Radio Interface Protocol Architecture, 3GPP TS 25.301 v3.6.0, France, September 2000, describes an overall protocol structure of a Universal Mobile Telecommunications System (UMTS). There are three protocol layers:                physical layer, layer 1 or L1,        data link layer, layer 2 or L2, and        network layer, layer 3 or L3.        
Layer 2, L2, and layer 3, L3 are divided into Control and User Planes. Layer 2 consists of two sub-layers, RLC and MAC, for the Control Plane and four sub-layers, BMC, PDCP, RLC and MAC, for the User Plane. The acronyms BMC, PDCP, RLC and MAC denote Broadcast/Multicast Control, Packet Data Convergence Protocol, Radio Link Control and Medium Access Control respectively.
FIG. 2 displays a simplified UMTS layers 1 and 2 protocol structure for a Uu Stratum, UuS, or Radio Stratum, between a user equipment UE and a Universal Terrestrial Radio Access Network, UTRAN.
Radio Access Bearers, RABs, are associated with the application for transportation of services between core network, CN, and user equipment, UE, through a radio access network. Each RAB is associated with quality attributes such as service class, guaranteed bit rate, transfer delay, residual BER, and traffic handling priority. An RAB may be assigned one or more Radio Bearers, RBs, being responsible for the transportation between UTRAN and UE. For each mobile station there may be one or several RBs representing a radio link comprising one or more channels between UE and UTRAN. Data flows (in the form of segments) of the RBs are passed to respective Radio Link Control, RLC, entities which amongst other tasks buffer the received data segments. There is one RLC entity for each RB. In the RLC layer, RBs are mapped onto respective logical channels. A Medium Access Control, MAC, entity receives data transmitted in the logical channels and further maps logical channels onto a set of transport channels. In accordance with subsection 5.3.1.2 of the 3GPP technical specification MAC should support service multiplexing e.g. for RLC services to be mapped on the same transport channel. In this case identification of multiplexing is contained in the MAC protocol control information.
Transport channels are finally mapped to a single physical channel which has a total bandwidth allocated to it by the network. In frequency division duplex mode, a physical channel is defined by code, frequency and, in the uplink, relative phase (I/Q). In time division duplex mode a physical channel is defined by code, frequency, and timeslot. As further described in subsection 5.2.2 of the 3GPP technical specification the L1 layer is responsible for error detection on transport channels and indication to higher layer, FEC encoding/decoding and interleaving/deinterleaving of transport channels.
None of the cited documents above discloses a method and system for interaction between radio resource management/radio link layer and transport protocol dynamics.